Over the last few years, digital printing has continually expanded its profile in the world of industrial marking. In 2019, the entire digital printing market was valued at $17.19 billion. By 2027, experts predict that this value will reach up to $45.69 billion. What is driving this rapid market growth? Digital printing offers advantages that conventional analog printing can’t match.

As compared to analog methods, such as flexo printing and lithography, digital printing is more versatile and often more cost-effective. Digital printing hardware carries lower upfront costs and doesn’t require the use of printing plates to replicate an image. Instead, digital printers source their images from electronic files. The files are easily prepared, simple to edit, and can be placed on a variety of substrates on-demand. These substrate options range from porous materials, like paper and cardboard, to non-porous materials, like metals and glass. 

Among these options, one of the most common digital printing applications today is marking transparent plastic sheets, more commonly known as plastic packaging film, flexible film, stretch film, stretch wrap, or shrink wrap. Each year, companies spend billions of dollars on plastic sheeting and films to house products for shipping, inventory, and retail purposes. For each of these contexts, the plastic must carry industry-mandated codes to enable traceability and educate consumers. With modern digital printers, this task is made simple. There are two distinct digital printing operations for plastic sheeting. One type of digital printing happens at the converter for decorating and branding of the sheeting. The second common type of digital printing for plastic sheeting happens during the packaging process where variable information such as date codes, lot numbers, and shift codes are printed.

Below are three of today’s most effective solutions for digital printing on transparent plastic sheets.

Solution 1: Thermal Inkjet Printers for Small Text and Images at Intermittent Speeds

Thermal inkjet (TIJ) printers have been a mainstay of digital printing since first entering the market in the 1980s. Lightweight and highly portable, TIJ printers are great for when companies need a machine that can be easily moved along production lines or operated in a handheld manner. 

In decades past, TIJ printers were unable to print on plastic or any non-porous substrate. Plastic sheeting being a particularly difficult substrate as the product moves between a web of rollers very quickly intermittent or continuously. If the ink is not dry then the print will be picked off, smudged, or offset by the rollers. TIJ printers use compact cartridges as an ink source, and older TIJ technology couldn't support the solvent-based ink formulas that make non-porous printing possible. Non-porous substrate printing was not viable as HP had not developed the 45si cartridge and the Funai cartridge was not available. However, as recent advancements in cartridge design and dry time have allowed for certain TIJ models like the Markem-Imaje 1200 and Anser X1 to use solvent-based inks perfect for metal, glass, and plastic sheets.

Today's TIJ printers offer:

• Lightweight construction, generally around five pounds due to a hardware design that separates pen stems from the controllers.
• Moderate printing speeds, at around 120 m/min—ideal for intermittent usage 
• High-resolution coding, often up to 600 x 300 DPI
• Zero-maintenance operation, as the removable cartridges eliminate the need for printhead services 

Solution 2: Continuous Inkjet and Binary Printers for Industrial Small Text Applications

While TIJ printers are reliable and capable of producing quality codes, they are not a great fit for high-speed production lines. For fast-moving, uninterrupted digital printing on transparent plastic sheets, both continuous inkjet (CIJ) and binary printers are better choices.

As the name suggests, CIJ printers operate by producing a continuous stream of pressurized ink. Within a CIJ printer is a system of pumps and valves that work together to move an ink mixture on a circular path from a reservoir to a printhead and the ink that did not deposit onto the substrate is then circulated back to the reservoir. Thanks to the circular ink path and constant pressurization, CIJ machines can print at high speeds without interruption.

With a CIJ printer, companies benefit from:

• High-speed printing, typically up to 1000 ft/min
• Continuous operation that can maximize uptime
• Environmental resistance due to the enclosed printhead and lack of internal heating elements

Binary printers, like the Domino Bitjet, are another great option for industrial small text applications. Like CIJ printers, binary printers offer high speeds and reliable mark consistency. Through the use of charge electrodes and electrostatic fields, binary printers are able to propel ink drops in precise patterns on substrates moving at over 2000 feet per minute. 

It’s also important to note that many TIJ, CIJ, and binary printers have difficulty auto-recognizing transparent substrates. To improve substrate recognition, operators can utilize photoelectric sensors, which are also known as photo-eyes, alongside their inkjet printers. 

Solution 3: Digital Inkjet Label Press for Large-Scale Printing

Both TIJ and CIJ printers are excellent at placing variable data such as small text and simple graphics on plastic sheets. However, their nozzle sizes prevent them from applying larger codes and images onto substrates. Digital label presses are more beneficial for these larger applications specifically for graphical decorating at the time of converting.

Rather than using a single nozzle to mark materials, digital label presses like Domino’s N610i use a series of printheads to increase image quality and size. Plastic sheets are fed into the press through a system of rollers. The web of rollers creates the optimal amount of surface tension in the sheets as they move towards the printheads. The multi-printhead layout allows digital presses to create exceptionally high-resolution images—up to 1200 x 1200 DPI. 

Although presses are incredibly powerful machines, they are also large and expensive. If companies do not require converting material upstream in the printing process then, a TIJ or CIJ printer will be a better option for the packaging operation. 

Digital Printing on Transparent Plastic Sheets Doesn't Have to Be Difficult

While printing on clear plastic may have been difficult in the past, cutting-edge digital solutions have made the application simple to complete. Technologies like TIJ printers, CIJ printers, and inkjet printing presses provide companies with different options to benefit their operations. 

Whether you need to code plastic by hand, mark hundreds of sheets along a high-speed line, or create incredibly high-resolution images, the coding and marking market has a way to make it easy.

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